1. Field of the Invention
The invention relates generally to automatic storage and retrieval systems, and more particularly to shuttle mechanisms used on storage and retrieval machines.
2. Reference to Prior Art
Automatic storage and retrieval systems are used in material and inventory storage facilities such as warehouses in which objects are to be temporarily stored. A known storage and retrieval system includes storage racks defining storage compartments or locations suited to hold a box, pallet or other object. The storage and retrieval system also includes a storage and retrieval machine that is moveable up and down an aisle between storage racks and that is operable to deposit objects in designated storage locations in the rack on either side of the aisle and to retrieve those objects when desired.
The storage and retrieval machine includes a base supported for horizontal movement along a track extending down the aisle. A mast extends upwardly from the base and supports a carriage for vertical movement relative to the storage racks. The carriage supports an extractor or shuttle mechanism that is horizontally extendable and retractable relative to the storage locations to remove objects from or place objects onto the racks. The storage locations are vertically separated by a distance sufficient to accommodate the shuttle mechanism when it is extended beneath an object to be moved.
Storage and retrieval machines capable of reaching two or three storage locations deep are also known. The shuttle mechanisms used in multi-reach storage and retrieval machines include a number of overlaid plate assemblies supported on rollers for extension in telescoping relation to one another to achieve the desired reach. Because of the number of plate assemblies needed to provide extended reach capabilities, multi-reach shuttles have a greater height than do single-reach shuttles. To accommodate the increased height of the shuttle, storage locations must be enlarged. This reduces the available vertical rack space for storing objects. For that reason, multi-reach shuttles are typically limited to double-reach depth. Further disadvantages associated with multi-reach shuttles include the size, cost and weight of the shuttle mechanisms.